1. Field of the Invention
The present invention relates to a hollow screw cooling device and, more particularly, to a hollow screw cooling device that is easy to maintain and assemble.
2. Description of the Prior Art
The hollow screw is frequently used as the feed apparatus in high speed rotating machine such as the machining center. The hollow screw in the prior art is disclosed, for example, as the H-shaped hollow screw produced by NSK Ltd. The main structure of the hollow screw is shown in FIG. 4. Each end of the screw 90 is supported by a bearing device 91. The screw is driven to rotate by a driving source such as a servo motor and drives a table 93 fixed on a screw nut 92 to have linear reciprocal motion.
To follow the trend of high speed feed, the inner portion of the screw 90 is hollow. Coolant is forced to circulate within the screw 90 by, for example, a pump so as to bring out heat generated during high speed operation. A conduit 94 of a proper length is provided along the axial direction within the hollow screw 90. One end of the conduit 94 connects to a coolant inlet formed on one end of the screw 90; the other end connects to a coolant outlet 95 formed on the driven end of the screw 90. The coolant outlet 95 is fixed on an oil-proof base 96 on the inner side of the bearing device 91 over the driven end of the screw 90 and connects to the conduit 94 through a cross pipe 97.
A rubber seal 98 in close contact with the screw 90 is provided within the oil-proof base 96. The seal 98 is likely to get vulcanized after a certain period of use or damaged due to friction under high rotating speed, thus it has to be maintained or replaced periodically. Since the oil-proof base 96 is mounted on the inner side of the bearing device 91 on the driven end, the bearing device 91 on the driven end has to be taken off first so that the oil-proof base 96 can be disassembled to take off the seal 98 for maintenance or replacement. This process is very complicated and time-consuming, and a high precision adjustment has to be performed on the screw 90 again after putting back the bearing device 91. So the maintenance and replacement of the seal 98 require a technician skilled in the art spending a long time to finish the job. This does not only affect the efficiency of the machining center but also is not economical at all.
In view of the foregoing drawbacks of the hollow screw in the prior art, the inventor made efforts to modify and improve the structure and, after many years of hard working and researches, finally came up with the hollow screw cooling device.
It is an object of the present invention to provide a hollow screw cooling device, which does not need to take off components such as the bearing and being device while maintaining and replacing the seal. The maintenance operation is fairly simple and fast. Furthermore, there is no need to perform a high precision adjustment on the screw after putting back the seal and the oil-proof base. This maintenance operation can be done by ordinary staff, which greatly saves costs in human power and time.
Another object of the present invention is to provide a hollow screw cooling device, wherein a seal is installed on the end with a smaller diameter of the screw. The radius of the seal decreases. The angular speed of the rotating seal also decreases as the radius diminishes. Therefore, the abrasion of the seal can be slower while the seal lifetime can be elongated. At the same time, fewer seal maintenance and replacements are needed.
Moreover, the present invention provides a hollow screw cooling device, which has a fall cooling effect on the bearing device and bearing and elongates its lifetime.
The hollow screw cooling device achieving the above objects has a set of apertures formed on the oil-proof base. The base is fixed on the outer side of a bearing press board by screws going through the apertures and the through holes on the bearing press board. By taking off the fixing screws, the oil-proof base can be directly separated from the bearing device for seal maintenance and replacement without the need to disassemble other components such as the bearing and bearing device.